Whitelist adapter options and support extra options.

README.md

@@ -177,7 +177,7 @@ resource :users do
   get '/:id' do
     if conditional
       # uses UserSerializer and configured default adapter automatically
-      user
+      current_user
     else
       # uses specified serializer and adapter
       render current_user, serializer: ErrorSerializer, adapter: :attributes
@@ -186,6 +186,21 @@ resource :users do
 end
 ```
 
+```ruby
+# Adhoc serializer options can be specified in the body of the route
+resource :users do
+  get '/:id' do
+    render current_user, extra: { adhoc_name_option: 'value' }
+  end
+end
+
+class UserSerializer
+  def name
+    instance_options[:adhoc_name_option] # accessible in instance_options
+  end
+end
+```
+
 ### Custom Metadata
 
 ```ruby

lib/grape-active_model_serializers/endpoint_extension.rb

@@ -38,9 +38,14 @@ module Grape
     end
 
     def render(resources, extra_options = {})
-      extra_options.symbolize_keys!
-      env['ams_meta'] = extra_options.slice(:meta, :meta_key)
-      env['ams_adapter_options'] = extra_options.except(:meta, :meta_key)
+      options = extra_options.symbolize_keys
+      env['ams_meta'] = options.slice(
+        :meta, :meta_key
+      )
+      env['ams_adapter'] = options.slice(
+        :adapter, :serializer, :each_serializer
+      )
+      env['ams_extra'] = options[:extra]
       resources
     end
 

lib/grape-active_model_serializers/options_builder.rb

@@ -13,6 +13,7 @@ module Grape
           options.merge!(default_root_options) unless options.key?(:root)
           options.merge!(meta_options)
           options.merge!(adapter_options)
+          options.merge!(extra_options)
           options
         )
       end
@@ -57,16 +58,22 @@ module Grape
 
       def meta_options
         options = {}
-        ams_meta = env['ams_meta'] || {}
-        meta = ams_meta[:meta]
-        meta_key = ams_meta[:meta_key]
+        meta_options = env['ams_meta'] || {}
+        meta = meta_options[:meta]
+        meta_key = meta_options[:meta_key]
         options[:meta] = meta if meta
         options[:meta_key] = meta_key if meta && meta_key
         options
       end
 
       def adapter_options
-        env['ams_adapter_options'] || {}
+        env['ams_adapter'] || {}
+      end
+
+      def extra_options
+        options = env['ams_extra'] || {}
+        return options if options.is_a?(Hash)
+        raise 'Extra options must be a hash'
       end
     end
   end

spec/grape/active_model_serializers/options_builder_spec.rb

@@ -71,7 +71,7 @@ describe Grape::ActiveModelSerializers::OptionsBuilder do
     end
 
     context 'adapter options' do
-      let(:env) { super().merge('ams_adapter_options' => adapter_options) }
+      let(:env) { super().merge('ams_adapter' => adapter_options) }
       let(:adapter_options) { {} }
 
       context 'adapter' do
@@ -91,6 +91,39 @@ describe Grape::ActiveModelSerializers::OptionsBuilder do
           expect(options[:serializer]).to eq(serializer)
         end
       end
+
+      context 'each_serializer' do
+        let(:adapter_options) { { each_serializer: each_serializer } }
+        let(:each_serializer) { V2::UserSerializer }
+
+        it 'includes each_serializer as top-level option' do
+          expect(options[:each_serializer]).to eq(each_serializer)
+        end
+      end
+    end
+
+    context 'extra options' do
+      let(:env) { super().merge('ams_extra' => extra_options) }
+
+      context 'hash' do
+        let(:extra_options) { { extra: 'info' } }
+
+        it 'includes extra options in top-level options' do
+          expect(options.keys).to include(:extra)
+        end
+      end
+
+      context 'not a hash' do
+        let(:extra_options) { 'extra' }
+
+        it 'raises an exception' do
+          expect {
+            options
+          }.to raise_exception(
+            'Extra options must be a hash'
+          )
+        end
+      end
     end
   end
 end